For a desktop PC, a flatbed scanner and a software program called OpenBook work great. OpenBook is accessible for screen-reading software, but costs about $1,000.
A portable alternative to using a flatbed scanner is the Pearl Camera from Freedom Scientific that works with OpenBook. The Pearl costs $795.
All scanners have a tough time with curved surfaces like the binding of a book. One option best suited for book scanning is the OpticBook Scanner (Book edge scanner).
On the desktop Mac, you can use the Prizmo 3 app for $49.95 with a flatbed scanner.
Other options include ABBYY FineReader for Pro $199.99 and Express for $69.
Evernote on the MAC can be used for OCR scanning, but involves syncing to a server and waiting in queue.
Tablets and smart phones offer more affordable options.
People rave about the KNFB Reader app for a couple reasons. Normally this app costs $99, but sometimes goes on sale for $49.
The view finder option tells you about how much of the page you have in view, so you know whether you need to raise your phone higher.
The next best app for a tablet or smart phone is the Prizmo app for about $20. It does not give you as much information as the KNFB Reader, but does a good job.
Stability is an issue when scanning documents with a smart phone or tablet.
ScanJig Pro is a portable plastic stand that offers stability as you use your smart phone or tablet to scan documents. ScanJig Pro costs $40 at Amazon. You can probably get it for less at http://www.scanjig.com
Amazon has a photo so people with usable vision can see how ScanJig holds the document and the device.
Thank you to the Washington Council of the Blind and Deb Lewis from the University of Washington for the lively discussion on our February Assistive Technology forum.